Semiconductor light-emitting device and method for manufacturing the same

ABSTRACT

A method of making a semiconductor light-emitting device including (A) a light-emitting portion by laminating in sequence a first compound semiconductor layer, an active layer, and a second compound semiconductor layer; (B) a first electrode electrically connected to the first compound semiconductor layer; (C) a transparent conductive material layer on the second compound semiconductor layer; (D) an insulating layer on a transparent conductive material layer; and (E) a second reflective electrode that on the transparent conductive material layer and on the insulating layer in a continuous manner, wherein, that the areas of the active layer, the transparent conductive material layer, the insulating layer, and the second electrode S 1 , S 2 , S 3 , and S 4 , respectively are related as S 1 ≦S 2 &lt;S 3  and S 2 &lt;S 4 .

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.12/632,404, filed on Dec. 7, 2009, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentinvention claims priority to and contains subject matter related toJapanese Patent Application JP 2008-317083 filed in the Japan PatentOffice on Dec. 12, 2008, the entire contents of which being incorporatedherein by reference.

BACKGROUND

The present invention relates to a semiconductor light-emitting deviceand a method for manufacturing the semiconductor light-emitting device.

Semiconductor light-emitting devices such as light-emitting diodes(LEDs), for example, include a light-emitting portion 20 composed of aprojecting laminated body obtained by laminating an n conductivity typefirst compound semiconductor layer 21, an active layer 23, and a pconductivity type second compound semiconductor layer 22 in sequence ona semiconductor light-emitting device manufacturing substrate(hereinafter may be simply referred to as a substrate 10). A firstelectrode (n-side electrode) 41 is disposed on the substrate 10 or anexposed portion 21 a of the exposed first compound semiconductor layer21. A second electrode (p-side electrode) 130 is disposed on the topface of the second compound semiconductor layer 22. Such semiconductorlight-emitting devices can be classified into two types of devices suchas a semiconductor light-emitting device in which light from the activelayer 23 is emitted through the second compound semiconductor layer 22and a semiconductor light-emitting device in which light from the activelayer 23 is emitted through the first compound semiconductor layer 21(called a bottom emission type for the sake of convenience).

In a bottom emission type semiconductor light-emitting device of therelated art, normally, a reflecting electrode that reflects visiblelight from the active layer 23 is often used as the second electrode 130as shown in FIG. 10 to maintain high light-emitting efficiency. Thesecond electrode 130 as a reflecting electrode includes, for example, alower layer 131 composed of silver (Ag) and an upper layer 132 composedof nickel (Ni) (e.g., refer to C. H. Chou, et al., “High thermallystable Ni/Ag(Al) alloy contacts on p-GaN”, Applied Physics Letters 90,022102 (2007)). Herein, since the lower layer 131 is composed of silver(Ag), a high light reflectance can be achieved. In addition, since theupper layer 132 is composed of nickel (Ni), the degradation caused byoxidation of the lower layer 131 and the occurrence of migration areprevented. In the drawing, reference numeral 42 denotes an insulatinglayer and reference numerals 43A and 43B denote contact portions.

Normally, the upper layer 132 covers the lower layer 131. Herein, thedistance from the edge of the lower layer 131 to the edge of the upperlayer 132 is defined as D₁. The region of the upper layer 132 from theedge of the lower layer 131 to the edge of the upper layer 132 isreferred to as an upper layer protruding region for the sake ofconvenience. The distance from the edge of the upper layer 132 to theedge of the projecting laminated body is defined as D₂. The region ofthe projecting laminated body from the edge of the upper layer 132 tothe edge of the laminated body is referred to as a laminated bodyexposed region for the sake of convenience. The upper layer protrudingregion surrounds the lower layer 131 so as to form a frame. Thelaminated body exposed region surrounds the upper layer protrudingregion so as to form a frame.

SUMMARY

Normally, part of light emitted in the active layer 23 is reflectedbetween the laminated body and the substrate 10. When part of thereflected light reaches the upper layer protruding region, some of thepart of the reflected light is absorbed at the upper layer 132 composedof nickel and constituting the upper layer protruding region and thereminder is reflected. As described above, the upper layer protrudingregion functions as a light-absorbing region, thereby posing a problemin that the light extraction efficiency as the entire semiconductorlight-emitting device is reduced. Furthermore, an electric current isnot injected into the laminated body exposed region from the secondelectrode 130, thereby posing a problem in that current density isincreased at the light-emitting portion and thus the light-emittingintensity is decreased due to a luminance saturation phenomenon.

Typical values of D₁ and D₂ are 1 μm. Thus, in a large semiconductorlight-emitting device including a projecting laminated body having asize of about 0.35 mm×0.35 mm, the total area of the laminated bodyexposed region and the upper layer protruding region is at most 20 ofthe area of the projecting laminated body. However, in a minutesemiconductor light-emitting device including a projecting laminatedbody having a size of about 10 μm×10 μm, the total area of the laminatedbody exposed region and the upper layer protruding region accounts foras much as 64% of the area of the projecting laminated body. Therefore,the light reflecting effect produced by the lower layer 131 composed ofsilver (Ag) is decreased in such a minute semiconductor light-emittingdevice. Moreover, in such a minute semiconductor light-emitting device,the light extraction efficiency as the entire semiconductorlight-emitting device is further reduced, and the light-emittingintensity is further decreased due to a luminance saturation phenomenon.

Accordingly, it is desirable to provide a semiconductor light-emittingdevice having a structure and a construction that can prevent the lightreflecting effect of the second electrode from being decreased and cansuppress the occurrence of migration without causing a decrease in thelight extraction efficiency as the entire semiconductor light-emittingdevice and a decrease in the light-emitting intensity due to a luminancesaturation phenomenon. It is also desirable to provide a method formanufacturing such a semiconductor light-emitting device.

According to an embodiment of the present invention, there is provided asemiconductor light-emitting device including:

(A) a light-emitting portion obtained by laminating in sequence a firstcompound semiconductor layer having a first conductivity type, an activelayer, and a second compound semiconductor layer having a secondconductivity type that is different from the first conductivity type;

(B) a first electrode electrically connected to the first compoundsemiconductor layer;

(C) a transparent conductive material layer formed on the secondcompound semiconductor layer;

(D) an insulating layer composed of a transparent insulating materialand having an opening, the insulating layer being formed on thetransparent conductive material layer; and

(E) a second electrode that reflects light from the light-emittingportion, the second electrode being formed on the transparent conductivematerial layer exposed at a bottom of the opening and on the insulatinglayer in a continuous manner,

wherein, assuming that an area of the active layer constituting thelight-emitting portion is S₁, an area of the transparent conductivematerial layer is S₂, an area of the insulating layer is S₃, and an areaof the second electrode is S₄, S₁≦S₂<S₃ and S₂<S₄ are satisfied.

According to another embodiment of the present invention, there isprovided a method for manufacturing a semiconductor light-emittingdevice including the steps of:

(a) forming, in sequence, a first compound semiconductor layer having afirst conductivity type, an active layer, and a second compoundsemiconductor layer having a second conductivity type that is differentfrom the first conductivity type on a principal surface of asemiconductor light-emitting device manufacturing substrate;

(b) forming a transparent conductive material layer on the secondcompound semiconductor layer;

(c) forming an insulating layer on the transparent conductive materiallayer, the insulating layer being composed of a transparent insulatingmaterial and having an opening;

(d) forming a second electrode that reflects light from a light-emittingportion on the transparent conductive material layer exposed at a bottomof the opening and on the insulating layer in a continuous manner;

(e) bonding the second electrode to a supporting substrate and removingthe semiconductor light-emitting device manufacturing substrate; and

(f) patterning the first compound semiconductor layer, the active layer,the second compound semiconductor layer, and the transparent conductivematerial layer together with the insulating layer and the secondelectrode to obtain the light-emitting portion in which the firstcompound semiconductor layer, the active layer, and the second compoundsemiconductor layer are laminated in sequence,

wherein, assuming that an area of the active layer constituting thelight-emitting portion is S₁, an area of the transparent conductivematerial layer is S₂, an area of the insulating layer is S₃, and an areaof the second electrode is S₄, S₁≦S₂<S₃ and S₂<S₄ are satisfied.

In the semiconductor light-emitting device or the method formanufacturing the semiconductor light-emitting device according to anembodiment of the present invention (hereinafter may be collectivelycalled “the present invention”), the transparent conductive materiallayer preferably transmits 90% or more of light emitted from thelight-emitting portion. In other words, such a transmittance is a valueobtained by forming a thin film having the same material as thatconstituting the transparent conductive material layer and having thesame thickness as the transparent conductive material layer, applyinglight having the same wavelength as that emitted from the light-emittingportion to the thin film, and measuring the percentage (lighttransmittance) at which the thin film transmits the light. To achievesuch a light transmittance, the thickness of the transparent conductivematerial layer may be suitably determined and the material constitutingthe transparent conductive material layer may be suitably selected.Examples of the material constituting the transparent conductivematerial layer include not only metals such as gold (Au), nickel (Ni),and platinum (Pt) and metal oxides such as RuO₂ but also transparentconductive materials. Examples of the transparent conductive materialsinclude indium tin oxide (ITO) (including Sn-doped In₂O₃, crystallineITO, and amorphous ITO), indium zinc oxide (IZO), F-doped In₂O₃ (IFO),tin oxide (SnO₂), Sb-doped SnO₂ (ATO), F-doped SnO₂ (FTO), zinc oxide(ZnO) (including Al-doped ZnO and B-doped ZnO), spinel-type oxides, andoxides having a YbFe₂O₄ structure.

In the present invention including the above-described preferable form,the insulating layer can be composed of silicon oxide (SiO_(x)), siliconnitride (SiN_(y)), silicon oxynitride (SiO_(x)N_(y)), tantalum oxide(Ta₂O₅), zirconium oxide (ZrO₂), aluminum oxide (Al₂O₃), aluminumnitride (AlN), titanium oxide (TiO₂), magnesium oxide (MgO), chromiumoxide (CrO_(x)), vanadium oxide (VO_(X)), tantalum nitride (TaN), or adielectric multilayer film (for example, a dielectric multilayer filmhaving a structure obtained by alternately laminating thin films with alow refractive index composed of SiO₂ or the like and thin films with ahigh refractive index composed of TiO₂, Ta₂O₅, or the like). Thetransparent insulating material constituting the insulating layer ispreferably a material that transmits 95% or more of light emitted fromthe light-emitting portion. The insulating layer can be formed byvarious physical vapor deposition (PVD) methods or various chemicalvapor deposition (CVD) methods in accordance with the material to beused. The opening can be formed by a combined method of lithography andetching.

In the present invention including the above-described preferable formand structure, the second electrode is preferably composed of silver, asilver alloy, aluminum, or an aluminum alloy. Examples of the silveralloy include a silver alloy containing 1% or less by weight of indium(In) and a silver alloy containing 0.1 to 10% by weight of palladium and0.1 to 3% by weight of at least one element selected from copper,aluminum, gold, platinum, tantalum, chromium, titanium, nickel, cobalt,and silicon. An Example of the aluminum alloy includes an aluminum alloycontaining 5% or less of cobalt (Co), 5% of nickel (Ni), and 1% ofcarbon (C) on a molar basis.

In the present invention including the above-described preferable formand structure, light from the active layer is preferably emitted to theoutside through the first compound semiconductor layer.

In the method for manufacturing the semiconductor light-emitting deviceaccording to an embodiment of the present invention including theabove-described preferable form and structure, the second electrode canbe bonded to the supporting substrate by a method using an adhesive, ametal bonding method, a semiconductor bonding method, or ametal-semiconductor bonding method. The semiconductor light-emittingdevice manufacturing substrate can be removed by wet etching, dryetching, laser ablation, or heating. The first compound semiconductorlayer, the active layer, the second compound semiconductor layer, andthe transparent conductive material layer, or the insulating layer andthe second electrode can be patterned by dry etching such as reactiveion etching (RIE) or wet etching. Herein, the insulating layer and thesecond electrode may be patterned after the first compound semiconductorlayer, the active layer, the second compound semiconductor layer, andthe transparent conductive material layer are patterned. Alternatively,the first compound semiconductor layer, the active layer, the secondcompound semiconductor layer, and the transparent conductive materiallayer may be patterned after the insulating layer and the secondelectrode are patterned; bonding to the supporting substrate isperformed; and the semiconductor light-emitting device manufacturingsubstrate is removed. Furthermore, the first compound semiconductorlayer, the active layer, and the second compound semiconductor layer,and the transparent conductive material layer may be patterned in acontinuous manner (in this case, normally S₁=S₂). Alternatively, thetransparent conductive material layer may be patterned after the firstcompound semiconductor layer, the active layer, and the second compoundsemiconductor layer are patterned (in this case, normally S₁<S₂). Thefirst compound semiconductor layer, the active layer, and the secondcompound semiconductor layer may be patterned after the transparentconductive material layer is patterned; bonding to the supportingsubstrate is performed; and the semiconductor light-emitting devicemanufacturing substrate is removed (in this case also, normally S₁<S₂).

In the present invention including the above-described preferable formand structure, the transparent conductive material layer and the secondelectrode can be formed by various PVD methods, various CVD methods, orplating methods. Examples of the PVD methods include (a) various vacuumdeposition methods such as electron beam heating, resistance heating,flash deposition, and pulse laser deposition (PLD); (b) plasmadeposition; (c) various sputtering methods such as diode sputtering,direct current (DC) sputtering, DC magnetron sputtering, radio frequency(RF) sputtering, magnetron sputtering, ion beam sputtering, and biassputtering; (d) various ion plating methods such as a DC method, an RFmethod, a multi-cathode method, an activation reaction method, a hollowcathode discharge (HCD) method, an electric field deposition method, anRF ion plating method, and a reactive ion plating method; (e) ion vapordeposition (IVD). Examples of the CVD methods include atmosphericpressure CVD, reduced pressure CVD, thermal CVD, plasma CVD, photo CVD,and laser CVD.

In the present invention including the above-described preferable formand structure, the first electrode can be composed of, for example, Ti,TiW, TiMo, Ti/Ni/Au, Ti/Pt/Au, (Ti/)TiW/Pt/Au, (Ti/)TiW/Pd/TiW/Pt/Au,Al, an aluminum alloy, AuGe, or AuGe/Ni/Au. Note that the layerindicated on the left side of “/” is situated closer to the active layerthan that indicated on the right side of “/”. Alternatively, the firstelectrode can be composed of a transparent conductive material such asITO, IZO, ZnO:Al, or ZnO:B. For example, a contact portion (pad portion)constituted by a metal multilayer having a laminated structure of[adhesive layer (e.g., Ti layer or Cr layer)]/[barrier metal layer(e.g., Pt layer, Ni layer, TiW layer, or Mo layer)]/[metal layer havingcompatibility with mounting (e.g., Au layer)] such as Ti layer/Ptlayer/Au layer may be optionally disposed on the first electrode and thesecond electrode (including the extending portion thereof). The firstelectrode and the contact portion (pad portion) can be formed by variousPVD methods such as vacuum deposition and sputtering, various CVDmethods, or plating methods.

In the method for manufacturing the semiconductor light-emitting deviceaccording to an embodiment of the present invention including theabove-described preferable form and structure, examples of thesemiconductor light-emitting device manufacturing substrate include aGaAs substrate, a GaN substrate, a SiC substrate, an alumina substrate,a sapphire substrate, a ZnS substrate, a ZnO substrate, an AlNsubstrate, a LiMgO substrate, a LiGaO₂ substrate, a MgAl₂O₄ substrate,an InP substrate, a Si substrate, a Ge substrate, a GaP substrate, anAlP substrate, an InN substrate, an AlGaInN substrate, an AlGaNsubstrate, an AlInN substrate, a GaInN substrate, an AlGaInP substrate,an AlGaP substrate, an AlInP substrate, a GaInP substrate, and thesessubstrates each having a base layer or a buffer layer formed on thesurface (principal surface) thereof.

The semiconductor light-emitting device according to an embodiment ofthe present invention including the above-described preferable form andstructure or the semiconductor light-emitting device obtained by themethod for manufacturing a semiconductor light-emitting device accordingto an embodiment of the present invention (hereinafter may becollectively called “a semiconductor light-emitting device or the likeaccording to an embodiment of the present invention”) is first disposedon the semiconductor light-emitting device manufacturing substrate.However, the semiconductor light-emitting device manufacturing substrateis removed in the end. The semiconductor light-emitting device or thelike can be mounted on the mount substrate described below in the end.Examples of the supporting substrate and the mount substrate includeglass sheets, metal sheets, alloy sheets, ceramic sheets, plasticsheets, and plastic films. A wiring line may be disposed on thesupporting substrate to connect the second electrode or the firstelectrode to the wiring line.

Examples of the compound semiconductor layers including the active layerin the semiconductor light-emitting device or the like according to anembodiment of the present invention include GaN compound semiconductors(including an AlGaN mixed crystal, an AlGaInN mixed crystal, or a GaInNmixed crystal), GaInNAs compound semiconductors (including a GaInAsmixed crystal or a GaNAs mixed crystal), AlGaInP compoundsemiconductors, AlAs compound semiconductors, AlGaInAs compoundsemiconductors, AlGaAs compound semiconductors, GaInAs compoundsemiconductors, GaInAsP compound semiconductors, GaInP compoundsemiconductors, GaP compound semiconductors, InP compoundsemiconductors, InN compound semiconductors, and AlN compoundsemiconductors. Examples of the n-type impurities added to the compoundsemiconductor layers include silicon (Si), selenium (Se), germanium(Ge), tin (Sn), carbon (C), and titanium (Ti). Examples of the p-typeimpurities include zinc (Zn), magnesium (Mg), beryllium (Be), cadmium(Cd), calcium (Ca), barium (Ba), and oxygen (O). The active layer may becomposed of a single compound semiconductor layer or may have a singlequantum well structure (QW structure) or a multiple quantum wellstructure (MQW structure). The compound semiconductor layer includingthe active layer can be formed by metal-organic chemical vapordeposition (MOCVD or MOVPE), metal-organic molecular beam epitaxy(MOMBE), or hydride vapor phase epitaxy (HYPE) in which halogenscontribute to transportation or reaction.

Examples of gas used in MOCVD for forming the compound semiconductorlayer include common gases such as a trimethylgallium (TMG) gas, atriethylgallium (TEG) gas, a trimethylaluminum (TMA) gas, atrimethylindium (TMI) gas, and arsine (AsH₃). Examples of nitrogensource gas include an ammonia gas and a hydrazine gas. For example, whensilicon (Si) is added as n-type impurities (n-type dopants), amonosilane (SiH₄) gas may be used as a Si source, and, when selenium(Se) is added, a H₂Se gas may be used as a Se source. On the other hand,when magnesium (Mg) is added as p-type impurities (p-type dopants), acyclopentadienyl magnesium gas, a methylcyclopentadienyl magnesium gas,or a bis(cyclopentadienyl) magnesium (Cp₂Mg) gas may be used as a Mgsource, and, when zinc (Zn) is added, dimethylzinc (DMZ) can be used asa Zn source. In addition to Si, examples of n-type impurities (n-typedopants) include Ge, Se, Sn, C, and Ti. In addition to Mg, examples ofp-type impurities manufacturing of a semiconductor red light-emittingdevice, examples of usable gas include trimethylaluminum (TMA),triethylaluminum (TEA), trimethylgallium (TMG), triethylgallium (TEG),trimethylindium (TMI), triethylindium (TEI), phosphine (PH₃), arsine,dimethylzinc (DMZ), diethylzinc (DEZ), H₂S, hydrogen selenide (H₂Se),and biscyclopentanediethylzinc.

Specifically, a light-emitting diode (LED) can be obtained from thesemiconductor light-emitting device or the like according to anembodiment of the present invention. For example, the size of thelight-emitting diode is 3×10⁻¹¹ m²≦S₁≦3×10⁻⁷ m², preferably 1×10⁻¹⁰m²≦S₁≦1×10⁻⁹ m², where S₁ is an area of the active layer.

The semiconductor light-emitting device or the like according to anembodiment of the present invention may be mounted on the mountsubstrate. In this case, a plurality of semiconductor light-emittingdevices should be mounted on the mount substrate. The number ofsemiconductor light-emitting devices, the type thereof, the way ofmounting (arrangement), the pitch, and the like may be determined inaccordance with, for example, the specifications, usage, and functionsof products including the semiconductor light-emitting devices. Examplesof the products obtained by mounting the semiconductor light-emittingdevices on the mount substrate include an image display apparatus, abacklight using semiconductor light-emitting devices, and a lightingapparatus. For example, a device using nitride-based group III-Vcompound semiconductors can be used as a semiconductor redlight-emitting device (red light-emitting diode), a semiconductor greenlight-emitting device (green light-emitting diode), and a semiconductorblue light-emitting device (blue light-emitting diode). Furthermore, forexample, a device using AlGaInP compound semiconductors can be used as asemiconductor red light-emitting device (red light-emitting diode). Inaddition, specifically, a light-emitting diode (LED), an edge-emittingsemiconductor laser, a surface-emitting laser device (vertical cavitysurface emitting laser (VCSEL)), and the like can be obtained from thesemiconductor light-emitting device or the like according to anembodiment of the present invention.

In the present invention, the second electrode is formed on thetransparent conductive material layer exposed at a bottom of the openingand on the insulating layer in a continuous manner and is not directlyin contact with the light-emitting portion. Thus, the migration of amaterial (atoms) constituting the second electrode to the light-emittingportion can be prevented with certainty. In addition, since S₂<S₃ issatisfied, the occurrence of migration can be prevented with morecertainty as described below. Since S₂<S₄ is satisfied, the lightreflecting effect of the second electrode can be certainly preventedfrom being decreased. Furthermore, the satisfaction of S₁ S₂ does notcause a decrease in the light extraction efficiency as the entiresemiconductor light-emitting device and a decrease in the light-emittingintensity due to a luminance saturation phenomenon. If the value ofS₃/S₂ or S₄/S₂ is decreased to the limitation of alignment precision inmanufacturing, the size as the entire semiconductor light-emittingdevice can be decreased to its limitation and semiconductorlight-emitting devices can be formed at a narrower pitch even if theactive layer has the same area. Consequently, a larger number ofsemiconductor light-emitting devices can be obtained from a singlecrystal growth substrate. Accordingly, the manufacturing cost of thesemiconductor light-emitting device can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are conceptual diagrams of a semiconductorlight-emitting device of Example 1, and FIG. 1C is a sectional viewschematically showing the semiconductor light-emitting device of Example1;

FIGS. 2A and 2B are partial sectional views schematically showing alaminated body or the like for describing a method for manufacturing thesemiconductor light-emitting device of Example 1;

FIGS. 3A and 3B are partial sectional views schematically showing alaminated body or the like for describing a method for manufacturing thesemiconductor light-emitting device of Example 1 after FIG. 2B;

FIGS. 4A and 4B are partial sectional views schematically showing alaminated body or the like for describing a method for manufacturing thesemiconductor light-emitting device of Example 1 after FIG. 3B;

FIGS. 5A to 5D are conceptual diagrams showing modifications of thesemiconductor light-emitting device of Example 1;

FIGS. 6A and 6B are partial sectional views schematically showing asemiconductor light-emitting device or the like for describing a methodfor manufacturing an image display apparatus of Example 2;

FIGS. 7A and 7B are partial sectional views schematically showing asemiconductor light-emitting device or the like for describing a methodfor manufacturing the image display apparatus of Example 2 after FIG.6B;

FIGS. 8A and 8B are partial sectional views schematically showing asemiconductor light-emitting device or the like for describing a methodfor manufacturing the image display apparatus of Example 2 after FIG.7B;

FIG. 9 is a partial sectional view schematically showing a semiconductorlight-emitting device or the like for describing a method formanufacturing the image display apparatus of Example 2 after FIG. 8B;and

FIG. 10 is a partial sectional view schematically showing asemiconductor light-emitting device of the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described on the basis of Exampleswith reference to the drawings.

Example 1

Example 1 relates to a semiconductor light-emitting device according toan embodiment of the present invention and a method for manufacturingthe semiconductor light-emitting device. A semiconductor light-emittingdevice 1 in Example 1 is specifically composed of a light-emittingdiode.

As shown in FIG. 1A that is a conceptual diagram and FIG. 1C that is aschematic sectional view, the semiconductor light-emitting device 1 ofExample 1 includes:

(A) a light-emitting portion 20 obtained by laminating in sequence afirst compound semiconductor layer 21 having a first conductivity type(specifically, n type in Example 1), an active layer 23, and a secondcompound semiconductor layer 22 having a second conductivity type(specifically, p type in Example 1) that is different from the firstconductivity type;

(B) a first electrode (n-side electrode) 41 electrically connected tothe first compound semiconductor layer 21;

(C) a transparent conductive material layer 30 formed on the secondcompound semiconductor layer 22;

(D) an insulating layer 31 composed of a transparent insulating materialand having an opening 31 a, the insulating layer 31 being formed on thetransparent conductive material layer 30; and

(E) a second electrode (p-side electrode) 32 that reflects light fromthe light-emitting portion 20, the second electrode 32 being formed onthe transparent conductive material layer 30 exposed at a bottom of theopening 31 a and on the insulating layer 31 in a continuous manner.

Assuming that an area of the active layer 23 constituting thelight-emitting portion 20 is S₁, an area of the transparent conductivematerial layer 30 is S₂, an area of the insulating layer 31 is S₃, andan area of the second electrode 32 is S₄, S₁≦S₂<S₃ and S₂<S₄ aresatisfied. Specifically, S₁=S₂=9.6 μm×9.6 μm and S₃=S₄=10.0 μm×10.0 μmin Example 1.

Specifically, in Example 1, the first electrode 41 is formed on asurface of the first compound semiconductor layer 21 opposite to asurface of the first compound semiconductor layer 21 that contacts theactive layer 23. The compound semiconductors constituting the firstcompound semiconductor layer 21, the active layer 23, and the secondcompound semiconductor layer 22 are composed of Al_(x)Ga_(y)In_(1-X-Y)N(0≦X≦1, 0≦Y≦1, and 0≦X+Y≦1), and more specifically, the compoundsemiconductors are GaN compound semiconductors. That is to say, thefirst compound semiconductor layer 21 is composed of Si-doped GaN(GaN:Si), and the active layer 23 is composed of an InGaN layer (welllayer) and a GaN layer (barrier layer) and has a multiple quantum wellstructure. The second compound semiconductor layer 22 is composed ofMg-doped GaN (GaN:Mg). The light-emitting portion 20 has a laminatedstructure obtained by laminating the first compound semiconductor layer21, the active layer 23, and the second compound semiconductor layer 22.Furthermore, the first electrode 41 is composed of a metal laminatedfilm having a Ti/Pt/Au structure. The thicknesses of the Ti film and thePt film are, for example, 50 nm and the thickness of the Au film is, forexample, 2 μm. The transparent conductive material layer 30 is composedof a gold layer having a thickness of 2 nm. The insulating layer 31 iscomposed of silicon oxide (SiO_(x) and X=2 in Example 1) having athickness of 0.2 μm. The second electrode 32 is composed of a silveralloy having a thickness of 0.2 μm. The transmittance of light whosewavelength is 520 nm to a gold thin film having a thickness of 2 nm isabout 92%, and the sheet resistance of the gold thin film is 12Ω/square. The transmittance of the light to the insulating layer 31having a thickness of 0.2 μm is 99% or more, and the size of the opening31 a formed in the insulating layer 31 is 3 μm×3 μm. The lightreflectance of the second electrode 32 composed of a silver alloy isabout 95%. The light from the active layer 23 is emitted to the outsidethrough the first compound semiconductor layer 21.

In the semiconductor light-emitting device with a structure of therelated art shown in FIG. 10 (hereinafter referred to as a semiconductorlight-emitting device of Comparative Example 1), at least D₁=D₂=1.0 μmis necessary. Thus, in the semiconductor light-emitting device ofComparative Example 1, assuming that the size of the active layer is10.0 μm×10.0 μm, the size of the active layer in a portion into which anelectric current is injected from the upper layer 132 constituting thesecond electrode 130 is about 8 μm×8 μm. The size of the lower layer(light reflecting layer) 131 constituting the second electrode 130 is6.0 μm×6.0 μm.

When a value of the electric current that should be injected into thesemiconductor light-emitting device is 100 μA, the current density, theratio of a luminance saturation suppressing effect, and the ratio of thearea of the second electrode or the upper layer to the total area S₁ (10μm×10 μm) of the active layer in the semiconductor light-emittingdevices of Example 1 and Comparative Example 1 are shown in Table 1below.

TABLE 1 Current density Example 1: (100 × 10⁻⁶)/(9.6 × 9.6 × 10⁻⁸) = 109A/cm² Comparative Example 1: (100 × 10⁻⁶)/(8 × 8 × 10⁻⁸) = 156 A/cm²Ratio of luminance saturation suppressing effect due to current densitydecrease (light-emitting efficiency at current density in ComparativeExample 1 is 1.0) Light-emitting efficiency at current density inExample 1: 1.1 (actual value) Light-emitting efficiency at currentdensity in Comparative Example 1: 1.0 Area ratio of second electrode orupper layer Example 1: 100% Comparative Example 1: 36%

As described above, the current density can be decreased in thesemiconductor light-emitting device 1 of Example 1. The luminancesaturation suppressing effect in Example 1 is 1.1 times that inComparative Example 1. In addition, the area ratio of the secondelectrode to the active layer is 100%, which is 2.8 times the area ratioin Comparative Example 1. As a result, the optical output of thesemiconductor light-emitting device 1 can be increased.

As shown in FIG. 1B that is a conceptual diagram of the semiconductorlight-emitting device 1, when the semiconductor light-emitting device 1is operated, an electric field is formed from the second electrode 32 tothe transparent conductive material layer 30 through the insulatinglayer 31, and the electric field is concentrated at the edge of thetransparent conductive material layer 30. Although silver atomsconstituting the second electrode 32 migrate along the electric field,the migration is blocked by the insulating layer 31. The possiblemigration paths through which the silver atoms cross the insulatinglayer 31 are indicated by arrows labeled “migration” in FIG. 1B.However, since some of the migration paths are in the direction thatopposes the electric field, the silver atoms do not easily migrate inreality. In other words, the structure of the semiconductorlight-emitting device 1 of Example 1 shown in FIGS. 1A and 1C is astructure that can prevent the occurrence of migration with certainty.

In Example 1, the second electrode 32 is formed on the transparentconductive material layer 30 exposed at a bottom of the opening 31 a andon the insulating layer 31 in a continuous manner, and thus does notcontact the light-emitting portion 20. Therefore, the migration of amaterial (atoms) constituting the second electrode 32 to thelight-emitting portion 20 can be prevented with certainty. In addition,since S₂<S₃ is satisfied, the occurrence of migration can be preventedwith more certainty as described above. Since S₂<S₄ is satisfied, thelight reflecting effect of the second electrode 32 can be certainlyprevented from being decreased. Furthermore, the satisfaction of S₁≦S₂does not cause a decrease in the light extraction efficiency as theentire semiconductor light-emitting device and a decrease in thelight-emitting intensity due to luminance saturation phenomenon.

A method for manufacturing the semiconductor light-emitting device 1 ofExample 1 will now be described with reference to the drawings.

Step-100A

First, a first compound semiconductor layer 21A having a firstconductivity type, an active layer 23A, a second compound semiconductorlayer 22A having a second conductivity type that is different from thefirst conductivity type are formed in sequence on a principal surface ofa semiconductor light-emitting device manufacturing substrate 10.Because the first compound semiconductor layer 21A, the active layer23A, and the second compound semiconductor layer 22A are not yetpatterned, “A” is added at the end of their reference numeral. The sameis applied to reference numerals that denote each layer in the followingdescription. Specifically, the semiconductor light-emitting devicemanufacturing substrate 10 composed of sapphire is inserted into anMOCVD apparatus. After substrate cleaning is performed in a carrier gascomposed of hydrogen at a substrate temperature of 1050° C. for 10minutes, the substrate temperature is decreased to 500° C. On the basisof an MOCVD method, a trimethylgallium (TMG) gas that is a raw materialof gallium is supplied while an ammonia gas that is a raw material ofnitrogen is supplied, to perform crystal growth on a surface of thesemiconductor light-emitting device manufacturing substrate 10.Consequently, a base layer 11 composed of GaN is formed on the surfaceand the supply of the TMG gas is then stopped.

Step-100B

Subsequently, a light-emitting portion 20A obtained by laminating insequence an n conductivity type first compound semiconductor layer 21A,an active layer 23A, and a p conductivity type second compoundsemiconductor layer 22A is formed on the semiconductor light-emittingdevice manufacturing substrate 10.

Specifically, on the basis of the MOCVD method, crystal growth isperformed on the base layer 11 by increasing the substrate temperatureto 1020° C. and then supplying a monosilane (SiH₄) gas that is a rawmaterial of silicon at atmospheric pressure. Consequently, an nconductivity type first compound semiconductor layer 21A having athickness of 3 μm and composed of Si-doped GaN (GaN:Si) is formed on thebase layer 11. The doping concentration is, for example, about 5×10¹⁸cm⁻³.

After that, the supply of the TMG gas and the SiH₄ gas is temporarilystopped and the substrate temperature is decreased to 750° C. Bysupplying a triethylgallium (TEG) gas and a trimethylindium (TMI) gasthrough valve switching, crystal growth is performed to form an activelayer 23A composed of InGaN and GaN and having a multiple quantum wellstructure.

For example, a light-emitting diode with a light-emitting wavelength of400 nm is obtained by providing a multiple quantum well structure (e.g.,constituted by two layers of well) composed of GaN (thickness: 7.5 nm)and InGaN (thickness: 2.5 nm) having an In component of about 9%.Alternatively, a blue light-emitting diode with a light-emittingwavelength of 460 nm±10 nm is obtained by providing a multiple quantumwell structure (e.g., constituted by 15 layers of well) composed of GaN(thickness: 7.5 nm) and InGaN (thickness: 2.5 nm) having an In componentof 15%. A green light-emitting diode with a light-emitting wavelength of520 nm±10 nm is obtained by providing a multiple quantum well structure(e.g., constituted by 9 layers of well) composed of GaN (thickness: 15nm) and InGaN (thickness: 2.5 nm) having an In component of 23%.

After the active layer 23A has been formed, crystal growth is performedon the active layer 23A by stopping the supply of the TEG gas and theTMI gas, switching the nitrogen carrier gas to a hydrogen carrier gas,increasing the substrate temperature to 850° C., and then supplying aTMG gas and a bis(cyclopentadienyl) magnesium (Cp₂Mg) gas. Consequently,a second compound semiconductor layer 22A having a thickness of 100 nmand composed of Mg-doped GaN (GaN:Mg) is formed on the active layer 23A.The doping concentration is about 5×10¹⁹ cm⁻³. Subsequently, by stoppingthe supply of the TMG gas and the Cp₂Mg gas and decreasing the substratetemperature to room temperature, the crystal growth is completed.

Step-100C

After the completion of crystal growth, p-type impurities (p-typedopants) are activated by performing annealing treatment in a nitrogengas atmosphere at about 800° C. for 10 minutes.

Step-110

A transparent conductive material layer 30A composed of a gold thin filmhaving a thickness of 2 nm is formed on the second compoundsemiconductor layer 22A by vacuum deposition. Thus, a structure shown inFIG. 2A can be obtained.

Step-120

An insulating layer 31 composed of a transparent insulating material andhaving an opening 31 a is formed on the transparent conductive materiallayer 30A. Specifically, after an insulating layer 31 composed of SiO₂is entirely formed on the transparent conductive material layer 30A bysputtering, an opening 31 a is formed in the insulating layer 31 bylithography and RIE. Thus, a structure shown in FIG. 2B can be obtained.

Step-130

A second electrode 32A that reflects light from the light-emittingportion is formed on the transparent conductive material layer 30Aexposed at a bottom of the opening 31 a and on the insulating layer 31in a continuous manner by sputtering. Thus, a structure shown in FIG. 3Acan be obtained.

Step-140

The second electrode 32A and a supporting substrate 50 are attached toeach other through an adhesive layer 51 composed of an epoxy adhesive(refer to FIG. 3B). Subsequently, the semiconductor light-emittingdevice manufacturing substrate 10 is removed by mechanical polishing andwet etching.

Step-150

A patterned resist layer is formed on the exposed first compoundsemiconductor layer 21A by lithography. First electrodes 41 are thenformed on the first compound semiconductor layer 21A by liftoff usingthe resist layer.

Step-160

A patterned resist layer is formed on the exposed first compoundsemiconductor layer 21A by lithography. Subsequently, the first compoundsemiconductor layer 21A, the active layer 23A, the second compoundsemiconductor layer 22A, and the transparent conductive material layer30A are patterned by RIE with a Cl₂ gas using the resist layer as a maskfor etching. The resist layer is then removed.

Thus, as shown in FIG. 4A, a light-emitting portion 20 that is alaminated body constituted by a patterned first compound semiconductorlayer 21, a patterned active layer 23, and a patterned second compoundsemiconductor layer 22 can be obtained. In addition, a patternedtransparent conductive material layer 30 can be obtained. After that, apatterned resist layer is formed on the patterned light-emitting portion20 and the exposed insulating layer 31 by lithography. The insulatinglayer 31 and the second electrode 32A are patterned by RIE with an O₂gas and a CF₄ gas using the resist layer as a mask for etching. Theresist layer is then removed. Thus, a structure shown in FIG. 4B can beobtained. In the patterning described above, S₁≦S₂<S₃ and S₂<S₄ aresatisfied. The distance (formation pitch) between the centers ofsemiconductor light-emitting devices 1 adjacent to each other is 12.5μm.

The semiconductor light-emitting device 1 of Example 1 can bemanufactured through the steps described above.

Step-170

Subsequently, the supporting substrate 50 can be cut into semiconductorlight-emitting devices 1. Furthermore, various semiconductorlight-emitting devices (specifically light-emitting diodes) such as around lamp type device and a surface mounting type device can bemanufactured by performing resin molding and packaging.

A relationship between the area S₁ of the active layer constituting thelight-emitting portion, the area S₂ of the transparent conductivematerial layer, the area S₃ of the insulating layer, and the area S₄ ofthe second electrode is not limited to the above-described relationship.For example, S₁<S₂<S₃═S₄ may be satisfied as shown in FIG. 5A that is aschematic sectional view. Alternatively, S₁=S₂<S₃<S₄ may be satisfied asshown in FIG. 5B that is a schematic sectional view, or S₁=S₂<S₄<S₃ maybe satisfied as shown in FIG. 5C that is a schematic sectional view.Furthermore, a structure shown in FIG. 5D may be adopted when necessary.

Example 2

Example 2 is a modification of Example 1. In Example 2, thesemiconductor light-emitting devices 1 obtained in Example 1 arerearranged in an array (in a two-dimensional matrix) to manufacture, forexample, an image display apparatus. Specifically, in Example 2, thesteps described below are performed after Step-160.

Step-200

In this step, semiconductor light-emitting devices 1 are selected at adesired pitch. More specifically, semiconductor light-emitting devices 1are selected from many semiconductor light-emitting devices 1 that areobtained in Step-160 of Example 1 and are arranged in a two-dimensionalmatrix, at a pitch of every M devices in an X direction and every Ndevices in a Y direction. There are prepared a relay substrate 60 onwhich a weak adhesive layer 61 composed of silicone rubber is formed anda second relay substrate 70 in which an alignment mark (not shown)composed of a metal thin film or the like is formed in a predeterminedposition and on which an adhesive layer 71 composed of an uncuredphotosensitive resin is formed.

Examples of the material constituting the relay substrate 60 includeglass sheets, metal sheets, alloy sheets, ceramic sheets, semiconductorsubstrates, and plastic sheets. The relay substrate 60 is held by aposition determining apparatus (not shown). With the operation of theposition determining apparatus, the positional relationship between therelay substrate 60 and the supporting substrate 50 can be adjusted.

The adhesive layer 71 may be basically composed of any material as longas the material provides an adhesive function by some method. Forexample, materials providing an adhesive function through theapplication of energy beams such as light (particularly ultraviolet raysor the like), radial rays (X rays or the like), or electron beams, ormaterials providing an adhesive function through the application ofheat, pressure, or the like can be used. A resin adhesive layer,particularly a photosensitive adhesive, a thermosetting adhesive, or athermoplastic adhesive can be exemplified as a material that can beeasily formed and provide an adhesive function. For example, when aphotosensitive adhesive is used, an adhesive function can be provided toan adhesive layer by applying light or ultraviolet rays to the adhesivelayer or by applying heat thereto. When a thermosetting adhesive isused, an adhesive function can be provided to an adhesive layer byheating the adhesive layer through the application of light or the like.When a thermoplastic adhesive is used, by selectively heating part of anadhesive layer through the application of light or the like, the part ofthe adhesive layer can be melted to impart fluidity. In addition, forexample, a pressure-sensitive adhesive layer (e.g., composed of anacrylic resin) can be exemplified as an adhesive layer.

The selected semiconductor light-emitting devices 1 are transferred tothe relay substrate 60 such that the exposed first compoundsemiconductor layer 21 and the exposed first electrodes 41 contact therelay substrate 60. Specifically, the weak adhesive layer 61 is pressedagainst the semiconductor light-emitting devices 1 arranged on thesupporting substrate 50 in a two-dimensional matrix (refer to FIGS. 6Aand 6B). Subsequently, for example, an excimer laser is applied to thesemiconductor light-emitting devices 1 to be transferred from the backside of the supporting substrate 50 (refer to FIG. 7A). Consequently,laser ablation is caused and the semiconductor light-emitting devices 1to which the excimer laser has been applied are detached from thesupporting substrate 50. When the relay substrate 60 is separated fromsemiconductor light-emitting devices 1, only the semiconductorlight-emitting devices 1 detached from the supporting substrate 50become attached to the weak adhesive layer 61 (refer to FIG. 7B).

Step-210

The semiconductor light-emitting devices 1 are placed (moved ortransferred) on the adhesive layer 71 (refer to FIGS. 8A and 8B).Specifically, the semiconductor light-emitting devices 1 are placed onthe adhesive layer 71 of the second relay substrate 70 from the relaysubstrate 60 with reference to the alignment mark formed on the secondrelay substrate 70. Since the semiconductor light-emitting devices 1 areweakly attached to the weak adhesive layer 61, when the relay substrate60 is moved in the direction in which the relay substrate 60 is detachedfrom the second relay substrate 70 while the semiconductorlight-emitting devices 1 are in contact with (are pressed against) theadhesive layer 71, the semiconductor light-emitting devices 1 are lefton the adhesive layer 71. Furthermore, by deeply burying thesemiconductor light-emitting devices 1 in the adhesive layer 71 using aroller or the like, the semiconductor light-emitting devices 1 can betransferred to the second relay substrate 70.

A method using such a relay substrate 60 is called a step transfermethod for the sake of convenience. By repeating the step transfermethod a desired number of times, a desired number of semiconductorlight-emitting devices 1 are attached to the weak adhesive layer 61 in atwo-dimensional matrix and transferred to the second relay substrate 70.Specifically, in Example 2, 160×120 semiconductor light-emitting devices1 are attached to the weak adhesive layer 61 in a two-dimensional matrixin a single step transfer and then transferred to the second relaysubstrate 70. Therefore, 1920×1080 semiconductor light-emitting devices1 can be transferred to the second relay substrate 70 by repeating thestep transfer method (1920×1080)/(160×120)=108 times. In addition, byrepeating the above-described steps three times, a desired number ofsemiconductor red light-emitting devices (red light-emitting diodes),semiconductor green light-emitting devices (green light-emittingdiodes), and semiconductor blue light-emitting devices (bluelight-emitting diodes) can be transferred to the second relay substrate70 at a desired distance and pitch.

Subsequently, a photosensitive resin constituting the adhesive layer 71is cured by applying ultraviolet rays to the adhesive layer 71 on whichsemiconductor light-emitting devices 1 are arranged. Thus, thesemiconductor light-emitting devices 1 are fixed on the adhesive layer71. After that, the semiconductor light-emitting devices 1 aretemporarily fixed on a second substrate for temporal fixing through thefirst electrodes 41. Specifically, there is prepared a second substratefor temporal fixing composed of a glass substrate on which an adhesivelayer 80 composed of an uncured adhesive is formed. By bonding thesemiconductor light-emitting devices 1 and the adhesive layer 80 andthen curing the adhesive layer 80, the semiconductor light-emittingdevices 1 can be temporarily fixed on the second substrate for temporalfixing. Subsequently, the adhesive layer 71 and the second relaysubstrate 70 are removed from the semiconductor light-emitting devices 1by an appropriate method. In this state, the second electrode 32 of eachof the semiconductor light-emitting devices 1 is exposed.

Step-220

A second insulating layer 81 is entirely formed, and an opening 82 isformed in the second insulating layer 81 above the second electrode 32of each of the semiconductor light-emitting devices 1. A second wiringline 83 is formed so as to extend from a region on the second electrode32 to a region on the second insulating layer 81 through the opening 82.The second wiring line 83 extends in a direction perpendicular to thepaper surface of the drawing. Subsequently, the second insulating layer81 including the second wiring line 83 is bonded to a mount substrate 85composed of a glass substrate through an adhesive layer 84, whereby thesemiconductor light-emitting device 1 can be mounted (fixed) on themount substrate 85. Next, for example, an excimer laser is applied fromthe back side of the second substrate for temporal fixing. Consequently,laser ablation is caused and the semiconductor light-emitting device 1to which the excimer laser has been applied is detached from the secondsubstrate for temporal fixing. In this state, the first electrodes 41 ofthe semiconductor light-emitting device 1 are exposed. Subsequently, afirst insulating layer 86 is entirely formed, and an opening 87 isformed in the first insulating layer 86 on the first electrodes 41 ofthe semiconductor light-emitting device 1. A first wiring line 88 isformed so as to extend from a region on each of the first electrodes 41to a region on the first insulating layer 86 through the opening 87. Thefirst wiring line 88 extends in a left-right direction of the drawing.FIG. 9 is partial sectional view schematically showing such a structure.By connecting the first wiring line and the second wiring line torespective driving circuits by an appropriate method, a semiconductorlight-emitting device and an image display apparatus constituted by thesemiconductor light-emitting device can be completed. In thesemiconductor light-emitting device 1, light generated in the activelayer 23 is emitted in a downward direction of FIG. 9.

The present invention has been described on the basis of preferableExamples, but is not limited to such Examples. The structure andconstruction of the semiconductor light-emitting device, the materialconstituting the semiconductor light-emitting device, and themanufacturing conditions and various numerical values of thesemiconductor light-emitting device that have been described in Examplesare mere examples and can be suitably modified.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A method for manufacturing a semiconductor light-emitting devicecomprising the steps of: (a) forming, in sequence, a first compoundsemiconductor layer having a first conductivity type, an active layer,and a second compound semiconductor layer having a second conductivitytype that is different from the first conductivity type on a principalsurface of a semiconductor light-emitting device manufacturingsubstrate; (b) forming a transparent conductive material layer on thesecond compound semiconductor layer; (c) forming an insulating layer onthe transparent conductive material layer, the insulating layer beingcomposed of a transparent insulating material and having an opening; (d)forming a second electrode that reflects light from a light-emittingportion on the transparent conductive material layer exposed at a bottomof the opening and on the insulating layer in a continuous manner; (e)bonding the second electrode to a supporting substrate and removing thesemiconductor light-emitting device manufacturing substrate; and (f)patterning the first compound semiconductor layer, the active layer, thesecond compound semiconductor layer, and the transparent conductivematerial layer together with the insulating layer and the secondelectrode to obtain the light-emitting portion in which the firstcompound semiconductor layer, the active layer, and the second compoundsemiconductor layer are laminated in sequence, wherein, assuming that anarea of the active layer constituting the light-emitting portion is S₁,an area of the transparent conductive material layer is S₂, an area ofthe insulating layer is S₃, and an area of the second electrode is S₄,S₁≦S₂<S₃ and S₂<S₄ are satisfied.
 2. The method for manufacturing asemiconductor light-emitting device according to claim 1, wherein thetransparent conductive material layer transmits 90% or more of lightemitted from the light-emitting portion.
 3. The method for manufacturinga semiconductor light-emitting device according to claim 2, wherein thetransparent conductive material layer is composed of Au, Ni, Pt, ITO,IZO, or RuO₂.
 4. The method for manufacturing a semiconductorlight-emitting device according to claim 1, wherein the insulating layeris composed of silicon oxide, silicon nitride, silicon oxynitride,tantalum oxide, zirconium oxide, aluminum oxide, aluminum nitride,titanium oxide, magnesium oxide, chromium oxide, vanadium oxide,tantalum nitride, or a dielectric multilayer film.
 5. The method formanufacturing a semiconductor light-emitting device according to claim1, wherein the second electrode is composed of silver, a silver alloy,aluminum, or an aluminum alloy.